In one type of navigation system, the navigation system generates a navigation solution (for example, an estimate of position and/or velocity) based on information that is a function of time. In one example of such a navigation system, a programmable processor is programmed to generate a position and velocity estimate using an integration operation that is performed once every second. The time between successive integration operations is also referred to here as the “step size” of the integration and is used by one or more of the calculations that are performed during each integration operation. In one implementation of such a system, the step size is determined for each integration operation using the clock signal used by the programmable processor (also referred to here as the “processor clock signal”). In some applications, however, the integration operation performed by the system is especially sensitive to errors in the step size and, in such applications, using the processor clock signal to determine the step size for each integration operation may not result in a sufficiently accurate navigation solution due to clock drift in the processor clock information.